Method and apparatus for automatically terminating uncontrolled flow of well fluids from a subsurface formation

ABSTRACT

Disclosed is a self-contained, automatic valve assembly designed to be anchored at a subsurface location within a well conduit which extends into a subterranean formation employed as a reservoir to store pressurized natural gas. The valve is preferably supported by a retrievable packer which anchors the valve within the conduit and forms a seal to force gas flowing in the conduit to flow through the valve. Operation of the valve is governed by a pressure charged dome control which acts through a bellows to move a valve stem to the closed position to terminate flow through the valve when the flowing well pressure drops by a predetermined amount relative to the dome pressure. Compensating means included in the dome control permit the value of the flowing well pressure required to close the valve to be raised or lowered by controlling the pressure at the wellhead. In the method of the invention, the pressure acting on the dome control is automatically increased as gas is injected into the formation so that the differential between the dome pressure and the reservoir pressure remains at a substantially fixed value. During periods when gas is being removed from the well, the control pressure acting in the dome is periodically reduced by control of the wellhead pressure so that the valve remains open as the reservoir pressure falls. During gas injection or gas removal, the valve functions as a safety device and closes automatically to terminate well flow any time the flowing well pressure drops below the dome control pressure by an established value.

United States Patent [191 Johnson et al.

[ Aug. 6, 1974 METHOD AND APPARATUS FOR AUTOMATICALLY TERMINATING UNCONTROLLED FLOW OF WELL FLUIDS FROM A SUBSURF ACE FORMATION [75] Inventors: Joseph L. Johnson, Houston; Shelby L. Guidry, Conroe, both of Tex.

[73] Assignee: Udell Garrett, Inc., a Division of Macco Oil Tools, Inc., Houston, Tex.

[22] Filed: Apr. 9, 1973 [2]] Appl. No.: 349,009

[52] U.S. Cl 166/314, 166/224 S [51] Int. Cl E2lb 43/12 [58] Field of Search 166/72, 224 R, 224 S [56] References Cited UNITED STATES PATENTS 3,045,759 7/1962 Garrett et al. 166/224 S Primary Examiner-James A. Leppink Attorney, Agent, or FirmTorres & Berryhill 57 ABSTRACT Disclosed is a self-contained, automatic valve assembly designed to be anchored at a subsurface location within a well conduit which extends into a subterranean formation employed as a reservoir to store pressurized natural gas. The valve is preferably supported by a retrievable packer which anchors the valve within the conduit and forms a seal to force gas flowing in the conduit to flow through the valve. Operation of the valve is governed by a pressure charged dome control which acts through a bellows to move a valve stem to the closed position to terminate flow through the valve when the flowing well pressure drops by a predetermined amount relative to the dome pressure. Compensating means included in the dome control permit the value of the flowing well pressure required to close the valve to be raised or lowered by controlling the pressure at the wellhead.

In the method of the invention, the pressure acting on the dome control is automatically increased as gas is injected into the formation so that the differential between the dome pressure and'the reservoir pressure remains at a substantially fixed value. During periods when gas is being removed from the well, the control pressure acting in the dome is periodically reduced by control of the wellhead pressure so that the valve remains open as the reservoir pressure falls. During gas injection or gas removal, the valve functions as a safety device and closes automatically to terminate well flow any time the flowing well pressure drops below the dome control pressure by an established value.

16 Claims, 5 Drawing Figures PATENTEB 65174 SHEEI 2 BF 3 METHOD AND APPARATUS FOR AUTOMATICALLY TERMINATING UNCONTROLLED FLOW OF WELL FLUIDS FROM A SUBSURFACE FORMATION BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to automatic safety equipment designed to regulate the flow of fluids through a flow conduit. As used herein, the term fluid is intended to encompass both the liquids and gases. In the embodiment to be described, the present invention relates to a self-contained, automatically closing safety valve designed to be anchored in an inplace well casing extending into a natural gas storage reservoir to prevent the escape of stored gas through the casing following failure of or damage to the casing or the wellhead structure.

2. Description of the Prior Art During slack gas usage periods, gas produced in one geographical area is often piped to depleted gas formations located in northern climates where it is stored for use in the colder months. Well structures extending into these depleted formations often include only a single string of casing through which the gas is injected into the formation during the storage phase and through which gas is extracted during the usage phase. Regulatory agencies and sound practice require that automatic safety equipment be employed within the casing to automatically terminate gas flow from the reservoir in the event the wellhead structure or casing should fail or be damaged.

In order to prevent such automatic safety equipment from being damaged and to position the equipment in its most useful location, it is usually desirable that the equipment be positioned as far as possible below the surface of the well. Such placement protects the equipment from surface impact and minimizes the amount of casing exposed to the formation pressure when the valve is closed. Because the gas flows in one direction when it is being injected into the subsurface formation andin another direction when it is being extracted from the formation, subsurface valves employed as safety equipment in such cases must be capable of permitting such flow while maintaining their ability to close automatically in the event of uncontrolled flow.

Many automatic safety valves, such as that described in US. Pat. application, Ser. No. 153,617, are designed to close automatically when the well conduit pressure drops below a predetermined minimum value. Such pressure drops are associated with loss of a controlled back pressure on the formation caused by failure of the confining well structure. It is conventional in valves of this type to control the pressure at which the valve will close by controlling the value of the pressure charge placed in a gas filled control dome. When the pressure around the valve drops below a given level, the resulting differential between the dome and well pressures is sufficient to close the valve.

Valves operating on this principle require that a predetermined relatively small pressure differential exist between the dome pressure and the well pressure. If the well pressure substantially exceeds the dome pressure, the valve will not automatically close until a large amount of gas has been lost and the formation pressure falls considerably. Ideally, the valve should close immediately when the flowing well pressure acting externally of the valve falls by only a limited amount.

To ensure that a conventional valve closes quickly with any significant reduction in the flowing well pressure, it is necessary after a reservoir has been charged to a high pressure to remove the valve from its subsurface location and pressurize the dome to a pressure which is relatively close to the normal flowing well pressure. In another situation when the formation pressure falls below a given value due to normal withdrawal of the stored gas, the valve will automatically close. To reinitiate flow, the valve must again be retrieved and the dome pressure must be reduced below the normal flowing well pressure. A valve may have to be retrieved a number of times to reset the dome pressure as gas is introduced into or removed from the well. The dangers and inconvenience associated with the need to remove the valve for dome pressure adjustments are obvious.

Remote control of the pressure charge in subsurface fluid valves has been suggested for the purpose of maintaining a substantially constant back pressure on a subterranean petroleum formation. US. Pat. No. 3,045,759 is exemplary of this type system in which the formation pressure is employed to control opening and closing of the valve. When the valves of the system close due to a drop in formation pressure, they remain closed until the formation pressure increases to a predetermined value at which time the valves automatically reopen. While such systems eliminate many of the control problems associated with pressure charged control domes, they are not suited for use as safety valves. One of the primary problems in this latter regard is the automatic reopening of the valve after the reservoir pressure builds back up. If a safety valve of the type presently under consideration closed automatically due to wellhead damage and then opened in response to an increase in formation pressure, the valve would repeatedly open and close and the well fluids would intermittently flow through the damaged well.

SUMMARY OF THE INVENTION The control pressure dome of the present invention is equipped with a charge check valve and a discharge check valve which jointly function as a pressure compensating section. Each of the valves is spring biased toward closed position. When opened, the charge valve vents fluid from a compensator chamber into the dome and the discharge valve vents fluid from the dome into the compensator chamber. The compensator chamber is in continuous pressure communication with the downstream side of the safety valve even when the valve is closed.

In the valve of the present invention, the charge valve automatically opens so that the pressure in the dome may increase with increasing pressure in the reservoir. By this means, a fixed pressure differential is maintained between the dome and the increasing reservoir pressure. If the wellhead is damaged, the valve automatically closes when the flowing well pressure drops relative to the dome pressure by a relatively small selected value. During periods when the reservoir is being drained, the safety valve automatically closes when the flowing well pressure drops by the selected value. A new lower dome pressure is then established by manipulating wellhead controls to lower the downstream pressure until the pressure in the compensator chamber reservoir filling'stage, a drop in the flowing well pressure below the selected value automatically causes the valve to close.

With the described method and valve construction, it will be appreciated that flow through a well equipped with the present invention may be terminated automatically anytime a given pressure drop occurs relative to the dome pressure of the valve and that the dome pressure may be remotely changed by control of the pressure downstream from the valve. Moreover, the valve will remain closed, irrespective of changes in the reservoir pressure.

From the foregoing it will be appreciated that a primary object of the present invention is to provide means for remotely changing the internal dome or control pressure 'of a subsurface safety valve whereby the surface safety valve by controlling the pressure downstream of the closed valve.

Another object of the present invention is to provide a safety valve of the type described having means for reopening the closed valve by pressure applied downstream of the valve.

A related object of the present invention is to provide a valve in which the internal control pressure may be established by surface pressure control and in which the valve reopens in response to downstream rather than upstream pressure conditions.

Yet another object of the present invention is to provide a retrievable, automatic safety valve through which fluids may flow in either direction and-in which the control dome pressure may be remotely controlled by surface pressure operations to maintain a desired pressure differential between the dome and the changing pressure in a subsurface formation whereby the valve will automatically close whenever the flowing well pressure drops by a predetermined amount.

Other features, advantages and objects of the invention may be more fully appreciated from the following specification and the related drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial vertical section illustrating a well equipped with the valve assembly of the present invention;

FIG. 2 is a graphical illustration of an exemplary relationship between control dome pressure and flowing well pressure attainable with the apparatus and method of the present invention;

FIGS. 3A and 3B are vertical quarter sectional views illustrating respectively the upper and lower portions of a compensated, pressure responsive safety valve of the present invention, in closed position; and

FIG. 4 is a view similar to FIG. 3A illustrating the valve in open position.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENT The automatic safety valve assembly of the present invention is indicated generally at 10 in FIG. 1. Components included with the assembly 10 include a packer P, a valving section V, a control section C and a compensator section S. The assembly 10 is illustrated anchored in position at a subsurface location within a tubular well casing W. The packer P is of a conventional construction in which expansion of the packer seal forms a pressure-tight seal between the body of the packer and the surrounding walls of the casing W. Once set, the packer anchors the assembly in place and forces all well fluids moving through the casing W to flow through the valve section V.

The packer P may be similar to that described in US. Pat. No. 3,593,784, entitled Anchor Assembly For Well Tools Such As Packers And The Like or similar to that described in US. Pat. No. 3,633,670, entitled Tool String Assembly For Use In Wells. Any packer employed to anchor the valve mechanism within the casing W is preferably retrievable and includes a large central opening to permit relatively unimpeded flow of fluid through the assembly.

Details of the construction of the valve and control portions. of the present invention are illustrated in FIGS. 3A, 3B which show the valve components as they appear in a stabilized, closed position. The valve section V includes a tubular valve housing 11 which is threadedly engaged to the base of an adapter section 12. The adapter section 12 is in turn connected to the body or the packer P (not illustrated) to support the depending valve section V and control section C. A tubular control housing 13 is threadedly secured to the base of valve housing 11 and is employed to support and protect pressure responsive bellows, stabilizer and spring components.

A linearly movable valve stem 14 is carried within the valve housing 11 and is mounted to be moved axially within the tubular valve housing 11 under the influence of the bellows and spring control components contained within the control housing 13. The valve stem 14 is of composite construction and includes an upper sealing head 15 threadedly secured at its lower end to a recocking sleeve 17. The outer external surface of the head 15 is equipped with a circumferentially extending seal mount recess which supports an annular seal 18 of a suitable elastomeric material. The seal 18 encircles the head 15 and, when the valve stem 14 is in its uppermost axial position as illustrated in FIGS. 3A, 3B, the seal 18 is designed to engage and seal against a seating surface 19a formed in an annular seat body 19 to prevent flow through the valve.

When the valve stem 14 is in its lowermost axial position as illustrated in FIG. 4 of the drawings, circumferentially developed slots 21 formed through the walls of valve housing 11 communicate with the bore of the body 19 to provide a flow passage through the valve V. The flow passage permits liquids or gases in the casing W above and below the set packer to flow in either direction through the valve V and packer P.

The stem head 15 supports a depending, axially movable central shaft 23. A triggering sleeve mechanism 33 surrounding the shaft 23 is employed to control the radial movement of a plurality of metal spherical detent balls 34. The balls are positioned for radial movement in a bore a formed in a tubular skirt segment of the valve stem 15 and are designed to move into and out of engagement with a recess 11a formed along the internal-wall of valve housing 11. The triggering mechanism 33 also includes a downwardly and radially inwardly tapered annular shoulder section 33b formed along its outer surface which is employed to urge the detent balls 34 radially outwardly when the member 33 is moved axially downwardly. A helical spring 330 encircles the shaft 23 and is restrained at its upper end by engagement with the stem 15 and at its lower end by engagement with a shoulder 33d extending radially inwardly from the base of triggering sleeve 33. Axially extending bores 33e formed in the sleeve 33 prevent pressure differentials from developing across the sleeve which would impede its movement. As may be seen by reference to FIG. 3A, a shoulder 23a on the shaft 23 provides a lower limit to travel of the sleeve 33.

The opening and closing movements of the valve stem 15 through the housing 11 are provided by bellows and spring drives contained within the control housing 13. The bellows portion of the control C includes a lower bellows section 35 and an upper bellows section 36 which enclose lower and upper bellows areas B-1 and B-2 respectively. The areas B-1 and B-2 are completely filled with a non-compressible fluid such as a light weight oil to provide bellows protection in a manner to be described. The lower bellows section 35 is housed within a lower housing portion 13a and the upper section 36 is housed in an upper control housing portion 13b. The upper and lower housing portions are threadedly secured to a central housing member 13c.

' An alignment sleeve 37 is threadedly engaged to the central housing section 13c. The lower end of the sleeve includes a tubular body 37a which extends downwardly internally of the lower bellows area B-l. The lowermost end of bellows section 35 is secured to an end structure 38 which includes an upwardly directed sleeve 39 telescopically received within the alignment sleeve body 37a. A plurality of radial bores 37a and 38a extend through the components 37a and 39, respectively, to ensure complete filling of the internal areas of the bellows with the non-compressible fluid. A plug 40 is threadedly engaged with the lower end of end structure 38 to provide a filling opening through which the bellows areas may be filled with liquid. The bellows sections are joined to their end structures by a suitable leakproof means such as soldering or welding or otherwise and resilient annular O-ring seals are positioned between threadedly engaged components to provide a leakproof seal of the areas confined within the bellows.

An axially movable safety valving body 42 is mounted for axial movement within the fluid contained in the areas B-1 and B-2. The member 42 includes an annular resilient seal member 43 which is designed to be moved axially between a lower seating surface 44 formed along the upper axial end of alignment sleeve 37 and an upper seating surface 45 formed along an inwardly directed shoulder extending from an end structure employed to secure the lower end of the bellows section 36. A coil spring 46 mounted about a sleeve 46' biases the body 42 and seal 43 into engagement with the upper seating surface 45. The body 42 includes an upwardly extending tubular support section 47 which is surrounded by a teflon sleeve 48. The sleeve 48 acts as a smooth underlying surface against which the bellows section 36 may slide. Radial openings 47a extend through the sleeve 47 to ensure complete liquid filling of the area B-2. The upper end of sleeve 47 is threadedly engaged to an end member 49 which holds the sleeve 48 in place and also functions as an axial bearing member.

The top of bellows 36 is secured to an axially movable upper end assembly 50. A depending sleeve 51 threadedly engaged to the lower end of the assembly extends over a portion of the bellows 36 and terminates in a radially projecting shoulder 51a. The upper end of end assembly 50 is threadedly engaged to a bushing 53 which provides an upper restraining shoulder for a resetting spring 54. The lower end of spring 54 is mounted against an inwardly extending shoulder 17a formed on the recocking sleeve 17. A closure spring 55 is mounted about sleeve 51 between shoulders 17b and 51a which are movable relative to each other. Radial openings 17b extending through the sleeve 17 prevents a pressure differential from developing across the walls of the sleeve. Casing pressure is communicated into the control C through openings in a protective screen 13b which cover pressure communication ports 56. The ports 56 extend through the valving housing walls and communicate with a bellows control area B-3 formed between the bellows housing 13 and the outersurface of bellows section 36.

. The compensator section S of the assembly 10 is best illustrated by reference to FIG. 3B. The compensator includes a tubular housing secured to the housing section 13a by a coupling 71. A lower end member 72 secured to the housing 70 supports a filter element 72a and functions as a lower mount for a pressure line 73. The upper end of the line 73 connects to the body 19 and provides pressure communication with the downstream side of the valve. The filter 72a is held in position by a resilient metal snap ring 72b and is preferably saturated with a suitable oil.

A mount body 75 threadedly engaged to the coupling 71 supports both a charge check valve 76 and a discharge check valve 77 which provides one-way pressure communication between a bellows pressure dome area 84 and a compensator chamber B-5. 0 ring seals employed throughout the section S maintain pressure tight seals between connecting components.

Valve 76 is equipped with a helical spring 78 which biases an engagement piece 79 and ball 80 toward the valves closed position. An externally threaded adjustment member 81 may be rotated and moved axially through threads in the tubular body of the valve 76 to adjust the closing force exerted against the ball 80. The valve 77 which includes a spring 82, engagement piece 83, ball 84 and adjustment member 85 is similar in construction and operation to the valve 76. It will of course be appreciated that other types of charge and discharge valve means may be employed to perform the function of the valves 76 and 77.

In the operation of the assembly 10, the pressure of the gas in pressure dome 84 determines the pressure at which the valve will open and close. Under normal operating conditions where gas is being injected into the formation or is being extracted from the formation, the pressure in the well conduit and in area B-3, is greater than that in the dome area B-4 causing the bellows section 36 to contract and the section 35 to elongate or expand which in turns holds the valve stem 14 at its lower, open position. The pressure in control area B-3 is the same as that existing in the well casing below the packer P. When the casing pressure drops below the dome pressure, corresponding to failure of the casing or wellhead structure, the pressure in area B-3 falls. The decrease in pressure permits the gas charge in the dome B4 to foreshorten the bellows section 35 as illustrated in FIG. 3A. This movement of bellows section 35 causes bellows section 36 to elongate. The end assembly 50 is moved upwardly by elongation of bellows section 36 causing the bushing 53 to engage the base of trigger sleeve 33 and push it upwardly against the force of spring 330. Raising of the triggering mechanism 33 permits detent balls 34 to retract radially out of recess 11a which releases the valve stem 14 from the valve housing 11. During the initial portion of the upward movement of bellows section 36, spring 55 is compressed by the upward movement of shoulder 51a with respect to valve stem 14 which, until the balls 34 release the recess lla, remains stationary. When the balls 34 move out of the recess 11a, the compressed force of spring 55 is suddenly released to swiftly move the valve stem 14 upwardly through the surrounding housing 11 to provide a snap action closure. Immediately preceding closure, the bellows 35 is compressed as illustrated in FIG. 3A. The initial upward movement of the assembly 50 also compresses spring 33c. When the detent balls 34 are in their radially retracted position where they are held by engagement with the internal walls of the valve housing 11, the engagement between taper surface 33b and balls 34 retains the spring 33c in compressed condition.

After damage to the well structure has been repaired, the valve may be reopened by pressuring up from the wellhead. During the downward movement of the stem 14 as the valve is being reopened, the spring 33c remains compressed until the detent balls are aligned with detent recess 11a. At this point, the balls are free to move radially outwardly and the compressed force of spring 33c acts against the tapered surface 33b to push the balls outwardly into locking engagement with the recess 11a so that the valve is locked into the open position illustrated in FIG. 4. The resetting spring 54 is compressed during the return movement of the bellows 55 caused by the pressure increase in the well following valve closure. The force of the compressed spring is released to snap the stem 14 fully open during the resetting operation so that the valve closure surfaces are completely withdrawn from the valve flow passage.

Because the bellows section 35 and 36 may be exposed to extremely high pressure differentials, the control C is provided with a means for preventing over contraction or over expansion of the bellows sections which would permanently distort the bellows and thereby destroy them for their intended usage. This safety provision is provided by the safety valving sleeve 42. When the valve is open as illustrated in FIG. 4, the spring 46 is compressed and the sleeve 42 is held at its lowermost axial position. In this position, the seal 43 engages the lower seating surface 44 and pressure existing in the bellows area B-2 is isolated from that existing in the bellows area B-l. Since the upper section B-2 is filled with an incompressible fluid, extremely high pressures may be tolerated without damage to the bellows sections. In the absence of the protected seal provided by sleeve 42 and seal 43, high pressures in the upper bellows area 8-2 will be communicated to the bellows area B-l causing the lower bellows to over expand outwardly and the upper bellows to over contract inwardly. In the opposite situation, where the pressure in control area B-3 falls below a predetermined value, the bellows 36 elongates, the bellows 35 shortens and the valve sleeve 42 is automatically permitted to move upwardly under the influence of the spring 46 causing the seal 43 to seat against the upper seating surface 45. The incompressible fluid filling bellows area B-l prevents the dome charge from overcompressing the bellows 35 and the seal 43 prevents communication of the high pressures existing in bellows area 8-1 to bellows area B-2 which thereby protects bellows 36 from over extension outwardly. The bellows section 36, however, remains free to expand and contract within the limits required for proper operation of the valve. By this means, relatively high pressures may be employed in the pressure dome B-4 without damage to the bellows components.

Operation of the compensator may best be explained by assuming exemplary pressure values and following a standard charge and discharge cycle for a gas storage reservoir. With joint reference to FIGS. 2 and 3A, 3B, it is assumed that the storage reservoir pressure annularly varies from 500 PSI to 2,000 PSI and the spring 78 is adjusted to apply a 400 PSI closing force against the ball and the spring 82 is adjusted to apply a 200 PSI closing force against the ball 84. The graph line L-l represents the annual variation of reservoir pressure and the graph line L-2 represents the corresponding variation in the dome pressure area of a valve of the present invention during the same period and employing the method of the present invention.

During the time gas is being stored, the reservoir pressure increases and the charge check valve 76 admits gas to the dome, keeping dome pressure always within 400 PSI of the reservoir pressure. It will be appreciated that the gas applied to the area B-5 is supplied through the line 73 and filtered by the oil saturated filtering material 72a to prevent debris and other materials from interferring with proper operation of the compensator portion of the invention. The oil in the filter is employed to prevent the dry well gas from damaging the seals in the compensator.

When gas is withdrawn from the reservoir, reservoir pressure drops and when the pressure drops by 400 PSI below the previous maximum reservoir pressure value, the pressure in dome area B-4 is sufficient to cause the valve to close in the manner previously described. It will be appreciated that in order to resume normal withdrawal of gas from the reservoir, the dome pressure in B-4 must be lowered. This is effected by lowering the pressure above the closed valve by a minimum of 600 PSI. This lowered pressure is communicated via line 73 to chamber B-5 permitting dome pressure to bleed down through the valve 77 at least 400 PSI. Pressure above the valve is then increased to equalize the pressure across the valve which automatically resets the dome pressure 400 PSI lower than the shut in reservoir pressure and simultaneously allows the valve to reopen. Normal withdrawal may then continue until the flowing pressure is again reduced by another 400 PSI increment and the valve closes again. The foregoing procedure can then be repeated to reopen the valve. The stair step configuration in the line L-2 represents the periodic closing and reopening of the valve as the dome pressure is steadily decreasing. If desired, as the declining reservoir pressure approaches the dome pressure, field personnel may choose a convenient time to readjust the dome pressure using the described procedure without waiting for the valve to close automatically.

From the foregoing it will be appreciated that the safety valve of the present invention functions in such a way that the difference between reservoir and dome pressure never exceeds the differential settingof the charging compensator check valves. The safety valve therefore closes automatically anytime flow from the well creates pressure reduction to the extent that the flowing well pressure is equal to the dome pressure.

While the valve of the present invention has been described for use with a retrievable packer in a single conduit well, it will be appreciated that various other applications of the invention are possible. it will also be appreciated that the valve of the present invention may be used as a safety valve in conventional producing wells and its use is not limited to gas storage wells. In this latter application, the function of the bypass line 73 may be unnecessary if surface effected changes in the dome pressure are not required. A valve so constructed is simply inserted into the production well and the desired dome pressure is automatically established by the formation pressure. While the described modified use of the valve has the advantage of eliminating the presence of high dome pressures during the fabrication, transportation and retrieval of the valve, it is undesirable to the extent that the valve must be retrieved each time the dome pressure is to be reset. This resetting is, however, relatively easily accomplished in that the valve need only be retrieved, exposed to a lower pressure and reinserted into the well.

It is conventional in some well installations to land and lock the safety valve in a prepositioned polished bore nipple included as a part of the production tubing. When a well is so equipped, a locking mandrel with suitable packing is employed to retrievably anchor the valve in position and provide the required seal with the tubing string. Other means for operatively positioning the valve of the present invention in the proper location are also possible and the present invention is not intended to be limited by the positioning and anchoring means or methods. It is also possible to employ the teachings of the present invention with valve structures other than those described herein. By way of further example rather than limitation, a compensator equipped valve may be provided with a mechanically operable bypass which may be operated by a suitable surface operated wireline tool. Once opened, the bypass permits the downstream portion of the well conduit to communicate with the formation so that pressure across the safety valve is equalized. This in turn reopens the valve and sets the new dome pressure without the need for a source of pressure at the well surface.

The foregoing disclosure and description of the invention is illustrative and explanatory thereof, and various changes in the size, shape and materials as well as in the details of the illustrated construction may be made within the scope of the appended claims without departing from the spirit of the invention.

We claim:

1. An automatic safety valve for regulating flow of fluids from a well conduit extending into a subsurface formation comprising:

a. pressure actuated, subsurface safety valve means connected with said conduit, said valve means including movable valve closure means movable to a closed position for terminating fluid flow through said conduit;

b. gas filled dome control means included in said safety valve means and operatively connected with said valve closure means;

c. surface controlled, pressure operated compensator means included in said valve means and operatively connected with said dome control means for changing the pressure in said dome control means;

d. closing means included in said valve means and responsive to the pressure differential between the pressure in said dome control means and the flowing well pressure in said conduit for causing said valve closure means to move to said closed position; and

e. opening means included in said valve means and responsive to pressure applied to said conduit above said closed valve means for moving said valve closure means from closed to open position.

2. A safety valve as defined in claim 1 wherein-said compensator means includes:

a. discharge valve means connected with said dome control means and responsive to a predetermined pressure differential between said dome control means and the pressure in said conduit above said safety valve means for discharging gas from said dome control means whereby the pressure in said dome control means is reduced; and v b. charge valve means connected with said dome control means and responsive to a predetermined pressure differential between said dome control means and the pressure in said conduit for charging said dome control means with gas whereby the pressure in said dome control means is increased.

3. A safety valve as defined in claim 2 further includmg:

a. a compensator chamber included with said safety valve means in a pressure communication with said dome control means through opening of said charge and discharge valve means; and f b. pressure communication means included with said valve means for providing continuous pressure communication between said compensator chamber and the area in said conduit above said safety valve means.

4. A safety valve as defined in claim 3 wherein said charge and discharge valve means include:

a. spring bias means for urging said charge and discharge valve means to their closed position; and

b. adjustment means for altering the force exerted by said spring bias means.

5. A safety valve as defined in claim 1 including means for altering the value of the pressure differential required between the pressure in said dome control means and the flowing well pressure for causing said valve closure means to move to said closed position.

6. An automatic safety valve as defined in claim 1 wherein:

a. said safety valve means includes valve body means having a flow passage with inlet and outlet means extending through at least a portion of said valve body means;

b. said movable valve closure means is connected with said valve body means for opening or closing said flow passage to respectively permit or terminate the flow of fluids or gases through said flow passage;

c. a substantially circular valve seat surface is connected with said closure means and said flow passage; j

d. said valve closure means includes valve stem means including sealing means for sealingly engaging and disengaging said seat surface to respectively terminate or permit flow through said passage, said valve stem means and said seat surface being mounted for linear movement with respect to each other; and

e. said valve means includes surface operable anchoring andv sealing means for respectively anchoring said valve body at a subsurface location within a well conduit and forming a seal between said well conduit and said valve body means to prevent fluids or gases in said well conduit from flowing axially past said sealing means without first flowing through said flow passage whereby closure of said closure means may terminate flow of fluids or gases through said well conduit.

7. An automatic safety valve as defined in claim 6 wherein said anchoring and sealing means includes a retrievable packer means with radially expansible and retractable securing means, a radially expansible and retractable elastomeric seal and a flow opening extending axially through a supporting packer body.

8. An automatic safety valve as defined in claim 7 wherein:

a. said valve body means includes a substantially tubular valve housing means connected to and supported by said packer body;

b. said valve stem means is mounted for linear movement within said valve housing;

0. said seat surface is formed in said valve housing means and encircles said flow passage; and

(1. said inlet end of said flow passage opens through the walls of said valve housing and said flow passage outlet end opens into said packer flow opening.

9. An automatic safety valve as defined in claim 8 wherein said closing and opening means includes:

a. contractable and expansible bellows means for forming a pressure seal between first and second pressure areas;

b. first chamber means cooperating with said bellows means to form confining boundaries about said first pressure area;

c. compressed spring means; and

d. release means connected with said spring means for releasing said compressed spring means from its compressed position when movement of said bellows means exceeds a predetermined amount to thereby produce a fast, powering movement of said stem means to closed position.

10. An automatic safety valve as defined in claim 9 further including bellows protection means including a noncompressible fluid contained in this said bellows means, a first chamber means enclosed within a portion of said bellows means and filled with said fluid and a selectively closable safety seal means operable by motion of said bellows means to seal said fluid in said first chamber means whereby the portion of said bellows means surrounding said first chamber means is prevented from contracting when said safety seal means seals said first chamber means.

11. An automatic safety valve as defined in claim 10 wherein:

a. said bellows means includes a second enclosed bellows chamber means connected through said safety seal means with said first chamber means;

b. incompressible fluid is contained in said first and second chamber means; and

, c. said safety seal means is operable by movement of said bellows means to seal either said first or second chamber means whereby fluid in the unsealed chamber means is isolated from the fluid in the sealed chamber means to prevent contraction of the bellows means in said sealed chamber means beyond a predetermined maximum amount.

12. An automatic safety valve as defined in claim 9 wherein said release means includes:

a. radially movable detent means extending through said stem means and adapted when in radially extended position to engage and lock with said valve housing means for preventing relative axial movement between said stem means and said valve housing means to hold said closure means in open position; and

b. triggering means operable by movement of said bellows means for permitting said detent means to retract radially whereby said compressed spring means is suddenly released to snap said stem means into engagement with said seat means.

13. A safety valve as defined in claim 1 wherein said compensator means includes discharge valve means responsive to a predetermined pressure differential between said dome control means and the pressure in said conduit above said safety valve means for discharging gas from said dome control means whereby the pressure in said dome control means is reduced.

. 14. A safety valve as defined in claim 1 wherein said compensator means includes charge valve means responsive to a predetermined pressure differential between said dome control means and the pressure in said conduit for charging said dome control means with gas whereby the pressure in said dome control means is increased.

15. A method of regulating the automatic closure of a compensator equipped, pressure dome actuated subsurface safety valve disposed in a well conduit extending into a subsurface formation comprising the steps of a. reducing the flowing well pressure sufficiently to cause said safety valve to automatically close;

b. reducing the pressure in the conduit area above the closed safety valve sufficiently to permit the pressure in said dome to begin to reduce;

c. pressurizing the conduit area above the closed valve to reopen the valve; and

d. increasing the dome pressure to a predetermined operating value relative to the flowing well pressure.

16. A method as defined in claim 15 including the further step of increasing the operating pressure of the gas in the dome of the safety valve through said compensator as the pressure of the formation increases whereby a predetermined pressure differential is maintained between the operating dome pressure and the increasing formation pressure. 

1. An automatic safety valve for regulating flow of fluids from a well conduit extending into a subsurface formation comprising: a. pressure actuated, subsurface safety valve means connected with said conduit, said valve means including movable valve closure means movable to a closed position for terminating fluid flow through said conduit; b. gas filled dome control means included in said safety valve means and operatively connected with said valve closure means; c. surface controlled, pressure operated compensator means included in said valve means and operatively connected with said dome control means for changing the pressure in said dome control means; d. closing means included in said valve means and responsive to the pressure differential between the pressure in said dome control means and the flowing well pressure in said conduit for causing said valve closure means to move to said closed position; and e. opening means included in said valve means and responsive to pressure applied to said conduit above said closed valve means for moving said valve closure means from closed to open position.
 2. A safety valve as defined in claim 1 wherein said compensator means includes: a. discharge valve means connected with said dome control means and responsive to a predetermined pressure differential between said dome control means and the pressure in said conduit above said safety valve means for discharging gas from said dome control means whereby the pressure in said dome control means is reduced; and b. charge valve means connected with said dome control means and responsive to a predetermined pressure differential between said dome control means and the pressure in said conduit for charging said dome control means with gas whereby the pressure in said dome control means is increased.
 3. A safety valve as defined in claim 2 further including: a. a compensator chamber included with said safety valve means in a pressure communication with said dome control means through opening of said charge and discharge valve means; and b. pressure communication means included with said valve means for providing continuous pressure communication between said compensator chamber and the area in said conduit above said safety valve means.
 4. A safety valve as defined in claim 3 wherein said charge and discharge valve means include: a. spring bias means for urging said charge and discharge valve means to their closed position; and b. adjustment means for altering the force exerted by said spring bias means.
 5. A safety valve as defined in claim 1 including means for altering the value of the pressure differential required between the pressure in said dome control means and the flowing well pressure for causing said valve closure means to move to said closed position.
 6. An automatic safetY valve as defined in claim 1 wherein: a. said safety valve means includes valve body means having a flow passage with inlet and outlet means extending through at least a portion of said valve body means; b. said movable valve closure means is connected with said valve body means for opening or closing said flow passage to respectively permit or terminate the flow of fluids or gases through said flow passage; c. a substantially circular valve seat surface is connected with said closure means and said flow passage; d. said valve closure means includes valve stem means including sealing means for sealingly engaging and disengaging said seat surface to respectively terminate or permit flow through said passage, said valve stem means and said seat surface being mounted for linear movement with respect to each other; and e. said valve means includes surface operable anchoring and sealing means for respectively anchoring said valve body at a subsurface location within a well conduit and forming a seal between said well conduit and said valve body means to prevent fluids or gases in said well conduit from flowing axially past said sealing means without first flowing through said flow passage whereby closure of said closure means may terminate flow of fluids or gases through said well conduit.
 7. An automatic safety valve as defined in claim 6 wherein said anchoring and sealing means includes a retrievable packer means with radially expansible and retractable securing means, a radially expansible and retractable elastomeric seal and a flow opening extending axially through a supporting packer body.
 8. An automatic safety valve as defined in claim 7 wherein: a. said valve body means includes a substantially tubular valve housing means connected to and supported by said packer body; b. said valve stem means is mounted for linear movement within said valve housing; c. said seat surface is formed in said valve housing means and encircles said flow passage; and d. said inlet end of said flow passage opens through the walls of said valve housing and said flow passage outlet end opens into said packer flow opening.
 9. An automatic safety valve as defined in claim 8 wherein said closing and opening means includes: a. contractable and expansible bellows means for forming a pressure seal between first and second pressure areas; b. first chamber means cooperating with said bellows means to form confining boundaries about said first pressure area; c. compressed spring means; and d. release means connected with said spring means for releasing said compressed spring means from its compressed position when movement of said bellows means exceeds a predetermined amount to thereby produce a fast, powering movement of said stem means to closed position.
 10. An automatic safety valve as defined in claim 9 further including bellows protection means including a noncompressible fluid contained in this said bellows means, a first chamber means enclosed within a portion of said bellows means and filled with said fluid and a selectively closable safety seal means operable by motion of said bellows means to seal said fluid in said first chamber means whereby the portion of said bellows means surrounding said first chamber means is prevented from contracting when said safety seal means seals said first chamber means.
 11. An automatic safety valve as defined in claim 10 wherein: a. said bellows means includes a second enclosed bellows chamber means connected through said safety seal means with said first chamber means; b. incompressible fluid is contained in said first and second chamber means; and c. said safety seal means is operable by movement of said bellows means to seal either said first or second chamber means whereby fluid in the unsealed chamber means is isolated from the fluid in the sealed chamber means to prevent contraction of the bellows means in said sealed chamber means beyond a predetermined mAximum amount.
 12. An automatic safety valve as defined in claim 9 wherein said release means includes: a. radially movable detent means extending through said stem means and adapted when in radially extended position to engage and lock with said valve housing means for preventing relative axial movement between said stem means and said valve housing means to hold said closure means in open position; and b. triggering means operable by movement of said bellows means for permitting said detent means to retract radially whereby said compressed spring means is suddenly released to snap said stem means into engagement with said seat means.
 13. A safety valve as defined in claim 1 wherein said compensator means includes discharge valve means responsive to a predetermined pressure differential between said dome control means and the pressure in said conduit above said safety valve means for discharging gas from said dome control means whereby the pressure in said dome control means is reduced.
 14. A safety valve as defined in claim 1 wherein said compensator means includes charge valve means responsive to a predetermined pressure differential between said dome control means and the pressure in said conduit for charging said dome control means with gas whereby the pressure in said dome control means is increased.
 15. A method of regulating the automatic closure of a compensator equipped, pressure dome actuated subsurface safety valve disposed in a well conduit extending into a subsurface formation comprising the steps of: a. reducing the flowing well pressure sufficiently to cause said safety valve to automatically close; b. reducing the pressure in the conduit area above the closed safety valve sufficiently to permit the pressure in said dome to begin to reduce; c. pressurizing the conduit area above the closed valve to reopen the valve; and d. increasing the dome pressure to a predetermined operating value relative to the flowing well pressure.
 16. A method as defined in claim 15 including the further step of increasing the operating pressure of the gas in the dome of the safety valve through said compensator as the pressure of the formation increases whereby a predetermined pressure differential is maintained between the operating dome pressure and the increasing formation pressure. 